I'm only responsible for what I say, not for what you understand. Although as an author I am responsible for making readers understand--a reader who doesn't understand is an unhappy reader. (And there is some value to leaving some questions unanswered.
Use This Body Language Cheat Sheet to Decode Common Non-Verbal Cues - GREAT! (The attached image identifies helpful nonverbal signs that can allows us to better observe and understand what others really mean.